Product Description; Theory Of Operation For 2-Color Sensors - RayTek MARATHON FA Operating Instructions Manual

Product Description
2 Product Description
The Marathon FA/FR fiber optic series of instruments are high‐performance infrared thermometers.
Each has a front end consisting of a small, fixed focus optical head coupled to a rugged fiber optic
cable wrapped with a flexible stainless steel sheath. The fiber optic cable attaches to an electronics
enclosure, which can be mounted away from the hot, hostile environment. The electronics enclosure
can be connected to a computer with its two‐way RS485 interface.
Temperature measurements can be taken using either of the following modes:
•
1‐color mode (FA and FR sensors) – for standard temperature measurements. The 1‐color
mode is best for measuring the temperature of targets in areas where no sighting obstructions,
either solid or gaseous, exist. The 1‐color mode is also best where the target completely fills
the measurement spot and where the background or foreground are higher in temperature
than the target.
•
2‐color mode (FR sensors only) – temperatures are determined from the ratio of two separate
and overlapping infrared bands. The 2‐color mode is best for measuring the temperature of
targets that are partially obscured (either intermittently or permanently) by other objects,
openings, screens, or viewing windows that reduce energy, and by dirt, smoke, or steam in
the atmosphere. The 2‐color mode can also be used on targets that do not completely fill the
measurement spot, provided the background is much cooler than the target.
Each model operates as a temperature measurement subsystem consisting of optical elements, spectral
filters, detector, and digital electronics. All components are water‐tight NEMA‐4 (IEC 529, IP 65) rated
and are built to operate on a 100 percent duty cycle in industrial environments. Simultaneous analog
and digital outputs consist of standardized current signals commonly available for use with
computers, controllers, recorders, alarms, or A/D interfaces.
Model
FA1A, FA1B, FA1C
FA1G
FA2A, FA2B
FR1A, FR1B, FR1C
2.1 Theory of Operation for 2‐Color Sensors
Two‐color ratio technology makes possible accurate and repeatable temperature measurements that
are free from dependence on absolute radiated energy values. In use, a 2‐color sensor determines
temperature from the ratio of the radiated energies in two separate wavelength bands (colors). The
benefits of 2‐color sensors are that accurate measurements can be made under the following
conditions:
•
When the field of view to the target is partially blocked or obscured.
•
When the target is smaller than the sensor's field of view.
•
When target emissivities are low or changing by the same factor in both wavelength bands.
2
Description
1-color-sensor in spectral range of 1 µm
different temperature ranges
1-color-sensor specifically designed for measuring glass
1-color-sensor in spectral range of 1.6 µm
different temperature ranges
2-color-sensor in spectral range of 1 µm (nominal)
different temperature ranges
Table 1: Models
Marathon Series FA/FR